Porous fluid-cooled electrical conductors and method for making same

ABSTRACT

Disclosed are fluid-cooled, high-current capacity electrical conductors manufactured by spirally rolling or winding porous metal sheet into a desired shape.

United States Patent Long [ 51 Jan. 25, 1972 [54] POROUS FLUID-COOLED ELECTRICAL CONDUCTORS AND METHOD FOR MAKING SAME [72] Inventor: Hugh M. Long, Tonawanda, NY.

[73] Assignee: Union Carbide Corporation, New York,

[22] Filed: Nov. 10, 1969 [21] Appl. No.: 875,326

[52] [1.8. CI. "29/624, 29/1635 R, 29/599, 113/116 A, 174/15 C, 174/126 R, 174/DIG. 6

[51] Int. Cl.-. ..I*l0lb 13/00, l-IO5k 3/00 [58] Field of Search ...174/l5 C, 15 SC, 126 R, DIG. 6; 29/599, 163.5, 624; 113/116 A [56] References Cited UNITED STATES PATENTS Babigan 174/126 x Delon... ..174/l5 C UX Latham ..174/l5 FOREIGN PATENTS OR APPLICATIONS 1,490,519 6/1967 France ..1 74/15 C Primary Examiner-John F. Campbell Assistant Examiner-D. C. Reiley AttorneyPaul A. Rose, Thomas I. OBrien. John C. Le Fever and Lawrence C. Kastriner [57] ABSTRACT Disclosed are fluid-cooled, high-current capacity electrical conductors manufactured by spirally rolling or winding porous metal sheet into a desired shape.

6 Claims, 2 Drawing Figures PATENIED was 1972 SHEET 1 UF 2 ATTORW'LY POROUS FLUID-COOLED ELECTRICAL CONDUCTORS AND METHOD FOR MAKING SAME This invention relates to cyogenically-cooled electrical conductors and to a method for making same.

In superconducting power transmission systems the conducting metal must be arrangedsuch that resistive and conductive heat can be readily removed by cooling fluid provided to maintain the conductive metal at low or superconducting temperatures. It follows that conductors having high-heat transfer surface area per unit volume of conductor are desirable to ensure that resistive and conductive heat are removed efiectively. Although fluid-cooled electrical conductors are not new, the prior art has not disclosed a satisfactory fluidcooled conductor having extremely high-current capacity which can be simply manufactured.

An object of this invention is to provide a fluid-cooled electrical conductor having high-current-carrying capacity, which conductor can be easily manufactured.

Another object is to provide a method of making high-current capacity, fluid-cooled electrical conductors.

Other objects will be apparent from the disclosure, drawings and appended claims.

SUMMARY OF THE INVENTION Disclosed herein is a porous metal, fluid-cooled, electrical conductor comprising spirally wound electrically conductive porous metal sheet, means for introducing and removing electrical current joined to each end of such wound metal sheet; fluid-impermeable electrically nonconductive means disposed on at least the outer surface of such wound metal sheet; and fluid conduit means disposed at each end of said metal sheet arranged to introduce cooling fluid at one end and discharge warmed fluid at the other end of said wound porous metal sheet after flow therethrough. Such conductors can have longitudinally varying or constant cross-sectional areas.

Also disclosed herein is a method for manufacturing a porous metal, fluid-cooled, electrical conductor which comprisesi (a) providing electrically conductive porous metal sheet; (b) spirally winding said metal sheet about itself so that at least some portions of adjacent layers are contiguous, (c) metal bonding together contiguous layers of the wound metal sheets; (d) joining an electrically conductive end connector to each end of the wound porous metal sheet; (e) attaching fluid conduit means to each end of said wound porous metal sheet; and (f) covering the outer surface of said wound porous metal sheet with an electrically nonconductive, fluid-impermeable I material.

DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION It has been found that cryogen-cooled conductors capable of conducting many thousands of amperes of electricity can be made in relatively small size from porous metal sheet such as screen wire which is spirally wound into a desired shape. In operation, cryogenic coolant is passed through the porous conductor to cool same and to maintain a desired temperature profile therein. The spirally wound porous metalsheet forms an electrically conductive porous structure having a ratio of void space volume to total volume such that cooling fluidmay pass therethrough with low resistance. A useful void space range based on adequate heat transfer surface, low resistance to coolant flow and structural strength considerations has been determined from experiments and calculations to be about to 95 percent void. Although the preferred porous metal sheeting is screen wire, expanded metal sheeting, perforated metal sheeting and the like may also be used for constructing fluid-cooled electrical conductors of this invention.

Conductors of this invention may be manufactured with various cross-sectional shapes such as circular, annular, elliptical and substantially flat. Also, two or more such porous metal conductors can be concentrically arranged and cooled together or individually. In addition, should a longitudinally varying cross-sectional area be desired, the porous metal sheet can be cut to a pattern prior to spiral winding, which pattern when wound yields the desired cross-sectional area variation with conductor length.

The spirally wound porous metal conductor of this invention may have warm and cold ends each with cross-sectional areas which exceed the cross-sectional area of the central portion of the conductor. Although this particular configuration is a separate invention claimed in copending application Ser. No. 875,115 filed Nov. 10, I969, in'the name of Lester K. Eigenbroad the method of the instant invention may be used to manufacture a conductor of such configuration.

Improved transverse electrical conduction can be obtained by means of bonding contiguous windings together, e.g., by placing solder or other suitable electrically conductive bonding material on the metal screen wire in the area of varying cross section and bonding such contiguous screen wire windings subsequent to or during spiral winding of the conductor, for example, as by applying appropriate heat to soldercoated windings.

Fluid cooling can best be accomplished by covering the exposed conductor surface with an electrically nonconductive, fluid-impenneable material to ensure that cooling fluid will flow substantially longitudinally through the porous metal sheet thereof. Hollow conductors would have both their inner and outer surfaces covered.

Examples of nonconductive, impermeable covering materials are thin-walled heat-shrinkable plastic tubing, polyimide sheet film, polytetrafluorethylene sheet and polyurethane-impregnated crepe paper. Epoxy is a suitable sealant and adhesive.

End connectors which provide convenient electrical terminal connections to the porous metal conductor as well as distribute electrical current flow uniformly over the ends of the spirally wound porous metal sheet are a required part of this invention. Additionally, such end connectors can be arranged to permit passage of cooling fluid through the wound porous metal portion of the conductor by means of appropriate passage or conduit means within or attached to said end connectors. Bonding of the end connectors to the wound porous metal portion can be accomplished by soldering, metal casting or other metal bonding methods. The end connectors may be cast in contact with the wound porous metal sheet thereby achieving both the fabrication of the end connector and its bonding to the wound porous metal sheet in one step.

FIG. 1 depicts a manufacturing method of this invention. Screen wire sheet 1 has been partially wound around mandrel 2. This screen wire sheet has been cut in a triangular pattern at its end which, when completely wound will result in a varying cross-sectional area along the conductor length. To ensure transverse electrical conduction in the varying cross section portion of the conductor, rectangular patches of solder 3 have been bonded to the screen wire sheet such that when the screen wire is wound, the solder can be bonded to windings contiguous thereto by applying appropriate heat.

FIG. 2 is a longitudinal cross-sectional view of an embodiment of this invention comprising a wound screen wire conductor as shown in preparation in FIG. 1. The mandrel has been removed from screen wire portion 1 and replaced with an electrically nonconductive plug 5. Solder portions 3 are also shown in cross section. This conductor has its exposed surface covered with an electrically nonconductive, gas-impermeable covering 6 which is provided to ensure that cooling fluid which enters the conductor through conduit passage 7 mounted in electrically conductive end connector 8 passes through wound screen wire 1 and exits through conduit passage 9 in end connector 10. Polyurethane-impregnated crepe paper has been found to be a suitable covering material.

Terminal posts 12 and 13 are also mounted in end connectors 8 and respectively. End connectors 8 and 10 are bonded to wound screen wire 1 by means of solder. If a large inner diameter hollow conductor is desired, as would result from using a large diameter mandrel, the inner surface of such a spirally wound hollow conductor can be covered with an electrically nonconductive, fluid-impermeable material as is the outer surface, in lieu of the mandrel being replaced with a nonconductive plug.

EXAMPLE I In an example of the conductors of this invention, a conductor similar to that shown being wound in FIG. 1 may be prepared from spirally wound 90-10 brass, 30 mesh X 0.0135 inch diameter wire cut as shown in FIG. 1 to give a desired cross-sectional variation when wound. End connectors as shown in FIG. 2 may be of solid copper or copper alloy and such end connectors joined to the spirally wound metal screen wire by means of solder. Electrically nonconductive gas-impermeable covering also shown in FIG. 2 may be of polyurethane-impregnated crepe paper. Terminal posts as well as gas conduit means shown in FIG. 2 could also be of solid copper or copper alloy. The electrically nonconductive plug shown in FIG. 2 would preferably be made of polytetrafluoroethylene. Solder portions 3 shown in FIG. 2 may be heated subsequent to winding to achieve bonding of contiguous screen wire layers which as heretofore stated would improve transverse electrical conductivity in the screen wire portion of the conductor. The size of such a conductor would be determined by its service requirements.

Although preferred embodiments of the invention have been described in detail, it is to be understood that modifications and variations may be effected without departing from the spirit and scope of the invention.

I claim:

1. A method for manufacturing a porous metal, fluidcooled, electrical conductor which comprises:

a. providing electrically conductive porous metal sheet;

b. spirally winding said metal sheet itself so that at least some portions of adjacent layers are contiguous;

c. metal bonding together contiguous layers of the wound metal sheet; joining electrically conductive end connectors to each end of the wound porous metal sheet;

e. attaching fluid conduit means to each end of said wound porous metal sheet; and

f. covering the outer surface of said wound porous metal sheet with an electrically nonconductive, fluid-impermeable material.

2. A method as described in claim 1 wherein said metal sheet is spirally wound around a mandrel.

3. A method as described in claim 2 wherein the mandrel is removed subsequent to winding said porous metal sheet and replaced with an electrically nonconductive material.

4. A method as described in claim 1 wherein the electrically conductive porous metal sheet is cut in a desired pattern prior to step (b).

5. A method as described in claim 1 wherein step (f) comprises additionally covering the inner surface of a spirally wound hollow conductor with an electrically nonconductive, fluid-impermeable material.

6. A method as described in claim 1 wherein solder patches are bonded to said porous metal sheet prior to spiral winding and the wound sheet is thereafter heated as the metal bonding contiguous layers step (c).

' Y}lli UNITED STATES PATENT 'Q F CE CERTIFICATE OF CORRECTION v Patent N5. 3 636 ,620 Dated January 25, 1972 Invent:o r(s) Long It is certified. that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claiin 1(5) line 6 after "sheet" insert -'-about--'. 7

Signed andsealed this 1mm day of November 1972.

(SEAL) Attest:

v EDWARD MJLET ERJR. Q ROBERT GOTTSCHALK Attestlng Offmer Commissioner of Patents UNITED STATEfi L mme ewma QER'HFICATE @F QREQHN Patent No. 3,636 ,620 Dated January 25, 1972 Inventor(s) H. M; Long It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1(b) line 6 after "sheet" insert --about-.

Signed and sealed this lLLth day of November 1972.

(SEAL) Attest:

EDWARD M.FLETCER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. A method for manufacturing a porous metal, fluid-cooled, electrical conductor which comprises: a. providing electrically conductive porous metal sheet; b. spirally winding said metal sheet about itself so that at least some portions of adjacent layers are contiguous; c. metal bonding together contiguous layers of the wound metal sheet; d. joining electrically conductive end connectors to each end of the wound porous metal sheet; e. attaching fluid conduit means to each end of said wound porous metal sheet; and f. covering the outer surface of said wound porous metal sheet with an electrically nonconductive, fluid-impermeable material.
 2. A method as described in claim 1 wherein said metal sheet is spirally wound around a mandrel.
 3. A method as described in claim 2 wherein the mandrel is removed subsequent to winding said porous metal sheet and replaced with an electrically nonconductive material.
 4. A method as described in claim 1 wherein the electrically conductive porous metal sheet is cut in a desired pattern prior to step (b).
 5. A method as described in claim 1 wherein step (f) comprises additionally covering the inner surface of a spirally wound hollow conductor with an electrically nonconductive, fluid-impermeable material.
 6. A method as described In claim 1 wherein solder patches are bonded to said porous metal sheet prior to spiral winding and the wound sheet is thereafter heated as the metal bonding contiguous layers step (c). 